Beckwith M-0359 Syncrocloser ®  Application Guide for Check Plus Grid Connection Synchronization Check Relay Engineering

The voltage, frequency, and phase angle conditions at the moment of circuit breaker closing are directly related to system stability and equipment safety in key operations such as transmission line reclosing, substation busbar paralleling, and islanding system recovery. M-0359 Syncrocloser launched by Beckwith Electric ®  Check Plus is an all solid state synchronous inspection relay designed specifically for power transmission and primary distribution systems. It can detect the static phase angle on both sides of the fracture within 0.5 seconds, while monitoring voltage amplitude and frequency difference. It also supports dead wire/dead bus closing, remote phase angle setting offset, and SCADA analog output. This article is based on the official M-0359 application guide, providing a complete technical implementation manual for relay engineers from working principles, setting methods, external wiring, analog output configuration to on-site debugging and maintenance.

Product positioning and core features

M-0359 is a direct upgraded substitute for traditional electromechanical synchronous inspection relays (i.e. "synchronous inspection" relays), but its functionality far exceeds the latter. It not only has independently adjustable voltage upper and lower limits, voltage difference, frequency difference, and phase angle windows, but also adds dead line/dead bus closure and SCADA compatible analog output (phase angle, frequency difference, voltage and voltage difference on each side), allowing the dispatch center to monitor the status of both sides of the circuit breaker in real time and assist in decision-making.

Typical application scenarios:

Substation interconnection line circuit breaker - synchronously closes when there is static or rotating phase angle.

Operator's backup device - indicates the reason for lockout (voltage, frequency, or phase angle exceeding the limit) through status contacts, making it easy for the operator to adjust system parameters.

Backup of automatic synchronization device - such as in conjunction with Beckwith M-0193 Syncrocloser, M-0193 is responsible for rotating phase angle (island) closing, M-0359 is responsible for static phase angle (networking) or dead line/dead bus closing, complementing each other.

Core advantages:

All setting knobs are independent of each other and can be adjusted on-site without the need for additional instruments.

The power supply is taken from the higher voltage input of Line or Bus (automatically turned off when below 65V), with a power consumption of only 11VA (main input)+1VA (other side).

Fully sealed semiconductor devices, instrument grade resistive capacitive components, operating temperature range of -40~+80 ℃, suitable for harsh outdoor environments.

Both input and output have passed the ANSI/IEEE C37.90.1-1989 transient immunity test, with a ground withstand voltage of 1500V AC/1min. The Line/Bus voltage input transformer is isolated, and the grounding scheme is flexible.

Definition of Input, Output, and Terminal

M-0359 adopts a standard 19 inch chassis (2U height), and all external connections are completed through the rear terminal block (mainly TB1). The key terminal functions are as follows (see Figure 2 in the manual):

Terminal Function Description

TB1-1 Bus voltage input (hot end) 120V AC nominal, maximum continuous 145V, withstand 240V/1s

TB1-2 Bus Voltage Input (Neutral) -

TB1-3 Line Voltage Input (Neutral) -

TB1-4 Line voltage input (hot end) as above

TB1-5/6 Bus Voltage Analog Output 0~7.5V DC corresponds to 0~150V rms (Option 1) or Current Output (Option 2)

TB1-7/8 Line voltage analog output is the same as above

TB1-9/10 Delta V analog output 0~10V DC corresponding to 0~20V rms (standard range)

TB1-1/12 phase angle analog output 0~10V DC corresponds to 0~± 180 ° (absolute value output)

TB1-13 Analog Common Terminal (0V) All analog signals share ground

TB1-14/16 Dead Line/Dead Bus Enable Input Close Contact Enable Dead Line Close or Dead Bus Close respectively

TB1-15/21 phase angle limit offset input external contact point can reduce or expand phase angle setting value (choose variable ratio when ordering)

TB1-17/18/19 closing relay contact normally open dry contact, connected at 25A/250V DC, disconnected at 0.9A/120V DC (inductive)

TB1-20 status contact common terminal -

TB1-22/23 phase angle OK status relay closed indicates that the phase angle meets the requirements (light load, 1A/125V DC resistive)

TB1-24/26 synchronous check enable input high level (or contact) enable synchronous check function

TB3-c/D Delta F analog output 20V/Hz, 10V corresponds to 0.5Hz

Important notice: Both Line and Bus inputs need to pass through the PT secondary side (120V line voltage or phase voltage), and the two voltages are isolated from each other and can be connected to different grounding systems. All control inputs (dead line, dead bus, phase angle offset, synchronization enable) are external dry contacts or level signals (0V common terminal).

Simultaneous condition detection logic